Heretofore, there has been known an image display apparatus utilizing the migration or displacement of magnetic powders. As one alternative to white boards, the image display apparatus has already been introduced to the market in a system designed such that a mixture of a white liquid and a black magnetic powder is encased in cells with a honeycomb structure, and an image, such as a character or graphic image, is displayed by means of the magnetic powder magnetically drawn in one direction using a magnetic pen or a magnetic head. Such an image display apparatus has also been developed as a paper-like display (also referred to as “electronic paper”) which employs a structure designed such that microcapsule-shaped cells each containing a magnetic powder are applied on a PET (Polyethylene Terephthalate) film through a binder, and the magnetic powders in the microcapsules are displaced using a magnetic pen or the like to display an image, such as a character image.
These conventional apparatuses having a low-cost simple structure with excellent maintainability are also used as toys.
However, the following disadvantages are pointed out to the above conventional thin display sheet.
(1) The use of one pole in a magnetic dipole of a magnetic head or a magnetic pen causes difficulties in focusing a magnetic force in a small area to result in deteriorated resolution.
(2) It is difficult to concentrate a high magnetic field in a small area within a short period of time. This causes difficulties in bringing a magnetic powder into close contact with the wall of a honeycomb cell or a microcapsule and in obtaining a high contrast ratio.
(3) The use of a magnetic powder suspended by a while liquid causes the gradual displacement of the magnetic powder to result in deteriorated retentivity of a displayed character or graphic image.
(4) The use of a dipolar magnetic field causes increase in writing stroke to result in extremely deteriorated expression at edges of a character or the like.
(5) The inevitable existence of the connection areas between honeycomb cells or microcapsules causes difficulties in assuring density in a shadow region and precludes a possibility of increasing the density.
(6) The restriction in size of a honeycomb cell or a microcapsule imposes limitations on increasing resolution.
(7) The restriction in size of a honeycomb cell or a microcapsule imposes limitations on reducing the thickness of the sheet.
(8) As compared to a simple coating operation, the production process of honeycomb cells or microcapsules is liable to be complicated and increased in cost.
In view of the above circumstances, it is therefore a primary object of the present invention to provide a rewritable thin image display sheet, an image display apparatus and an image display system, capable of reliably displaying an image in a rewritable state while achieving a significantly simplified structure.
It is another object of the present invention to provide a rewritable thin image display sheet, an image display apparatus and an image display system, capable of reliably displaying an image with an enhanced resolution while achieving a significantly simplified structure.
It is still another object of the present invention to provide a rewritable thin image display sheet, an image display apparatus and an image display system, capable of reliably displaying an image while achieving a significantly simplified structure having a significantly reduced thickness.
It is yet another object of the present invention to provide a rewritable thin image display sheet, an image display apparatus and an image display system, capable of reliably displaying an image with an excellent gradation expression while achieving a significantly simplified structure.